Field of the Invention
The present invention relates to a valve timing control apparatus of an internal combustion engine for controlling closing/opening timing of an intake valve and an exhaust valve.
Description of Related Art
In the related art, a valve timing control apparatus which may change and control a relative rotation phase of a camshaft with respect to a sprocket to which torque is transmitted in a crankshaft by using torque of an electrical motor, is disclosed.
The valve timing control apparatus includes the electrical motor, a motor housing of which is synchronized with the crankshaft and rotated, and a deceleration mechanism that decelerates a rotational speed of the electrical motor to transmit it to the camshaft.
The deceleration mechanism includes an eccentric shaft to which torque transmitted from a motor shaft, a ring shape member that is integrated with the sprocket and includes inner teeth of a waveform shape provided on an inner circumferential surface thereof, a plurality of rollers that are installed between respective inner teeth of the ring shape member and an outer wheel of a ball bearing, and a cage that is installed at the camshaft to form gaps between respective rollers and to allow all of the rollers to move in a radial direction.
A plurality of rollers with different outer diameters are previously prepared, and then are selectively assembled according to a gap between an outer circumferential surface of the rollers and an inner surface of the inner teeth thereof to be an optimal gap.
However, in the conventional valve timing control apparatus described above, the rollers having different outer diameters are selectively assembled such that the gap therebetween is adjusted, but since precision of the outer diameters of respective rollers precision is limited, it is difficult to accurately adjust the gap (backlash).
Accordingly, torque variation caused at the camshaft due to a difference of the gap causes relatively strong impact sound between the outer circumferential surface of the respective rollers and the inner surface of the inner teeth, etc., thus quality thereof deteriorates.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.